调用系统的查找对话框

procedure TForm1.Button1Click(Sender: TObject);
begin
 with TDDEClientConv.Create(Self) do begin
   ConnectMode := ddeManual;
   ServiceApplication := 'explorer.exe';
   SetLink( 'Folders', 'AppProperties');
   OpenLink;
   ExecuteMacro('[FindFolder(, C:\DOWNLOAD)]', False);
   CloseLink;
   Free;
 end;
end;